Effect of Copper-Based Fungicide Treatments on the Quality of Hop Produced in the Northeastern United States

The quality of hops is dictated in large part by the content of flavor and aroma compounds. These compounds vary in concentration and are affected by agricultural practices. Previous research has found that the application of Bordeaux Mixture may impact the aroma quality of hops by altering concentrations of varietal thiols. The impact of copper fungicides other than Bordeaux Mixture and in hop production areas outside of the Pacific Northwest in the United States has yet to be evaluated. Herein we study the effects of application frequency of a copper (II) hydroxide fungicide on markers of hop quality in hops grown in the Northeastern United States. Copper fungicide application was found to significantly increase the total copper content of hop cones, regardless of application frequency; however, traditional markers of hop quality, including yield, essential oil composition, and acid content, were not affected. Beer consumers were unable to discriminate between beers dry-hopped with conventional or copper-treated hops based on aroma but were able to discriminate based on in-mouth perception. These findings suggest that the use of copper (II) hydroxide for the mitigation of fungal pathogens in hops grown in the Northeastern United States is unlikely to adversely affect final hop yield, acid content, or thiol quality.